This invention generally relates to metalworking, and more particularly to a method of machining a metal workpiece, such as a titanium workpiece, which reduces adhesive wear between a machine tool, or machine tool subassembly, and the metal workpiece during the machining thereof.
In the course of modern manufacturing, machine tools are employed to deform and to dimension metal to produce a part having a desired shape. A type of machine tool often used in this purpose is a lathe, which in its simplest form is a machine for holding and rotating a workpiece against a single-point cutting tool. By feeding the cutting tool into the workpiece and along a lathe axis of rotation, any desired cylindrical contour can be produced.
As is well known in the art, the principal components of the lathe are a bed, a headstock, a tailstock and a carriage. It has been discovered that when using a lathe to machine certain metals, such as titanium for example, adhesive wear, such as galling, occurs on the metal workpiece at its juncture with the non-driving end of the lathe, such as the tailstock or other workpiece support assembly employed by the lathe. This adhesive wear often causes the workpiece to eccentrically rotate about the lathe axis of rotation which causes the workpiece to be machined with dimensions which may be out of tolerance. In severe situations, the tailstock may bond to the workpiece.
As used herein, galling means a type of adhesive wear which is caused by an imbalance of electrons existing between two mating metal surfaces. In this regard, when material is subject to galling under low stresses, minute junctions form at contacting surfaces and small fragments of the metals become detached with subsequent movement. When material is subject to galling under high stresses, large junctions are formed, or actual seizure may occur between the materials.
The foregoing illustrates limitations known to exist in present methods for machining certain metals. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.